maria-discuss team mailing list archive

[Pierre <pierz@xxxxxxxxxx>]

Using this technique I have the same Issue. It's now running for severals hours, I'm at a 40% and 
looking at show full processlist, it's getting slower and slower. It will never finish.

I think there is a bug here.

Firstly, regardly the memory usage, It doesn't correctly use the buffer I did set, I think it's only 
using the key_buffer_size. myisam_sort_buffer_size or bulk_insert_buffer_size are not used on this task.

So what's happening ? When the RAM is full, mariadb is doing random access on the disk to sort and 
filter Go of data ! That's why my cpu was only used a few percent, the process was in i/o wait most 
of the time.

So what I am saying here is : mariadb can't crate UNIQUE keys/index if the rows doesn't fit in RAM.

However if I try to create a standard index (ie non unique), it works well and it's done in less 
than an hour.

ALTER IGNORE TABLE mytable ADD INDEX (c1), ADD INDEX(c2);
Query OK, 349086532 rows affected (44 min 25.21 sec)
Records: 349086532  Duplicates: 0  Warnings: 0

In this second usage case, Maria is doing a good work by using the myisam_sort_buffer_size. I think 
it's doing something like an external/merge sort, spliting the rows in part that fit in RAM, sorting 
them, merging them and creating index.

It was 100% cpu most of the time, when It was not it was because mysql was loading the rows in RAM 
from hard disk (and not doing a random access on the hard disk like in create unique index). So why 
UNIQUE index is not behaving the same way ?

It's easy to reproduce the bug, just create a binary file of 2 or 3 x size of RAM, then load data 
infile and try to create a UNIQUE index on it. It will never end.

>Am 10.02.2014 13:45, schrieb Pierre:
>> Mariadb is getting slower and slower when I'm inserting a massive amout of data. I'm trying to 
insert 166 507 066
>> rows (12go) using load data infile '' into an empty table. I splitted my file in 13 parts of the 
same size because
>> it was too long to insert in one shot. When I inserted more than 100M rows, it starts to be 
extremely slow.
>
>he reason are the permamently updated keys
>in general for large inserts on a new table
>
>UNIQUE KEY `p1` (`p1`),
>UNIQUE KEY `p2` (`p2`),
>
>* remove keyes
>* insert data
>* add kyes
>
>https://dev.mysql.com/doc/refman/5.5/en/insert-speed.html